Electric power switch with an electronic memory unit for parameters and conversion factors

ABSTRACT

An electrical power breaker includes an electronic protective device and an electronic memory. The memory is accommodated in the power breaker such that it is physically separated from said protective device, for operational data for the power breaker. Data security when using the additional electronic memory is increased by the electronic memory being connected to the protective device via a data bus, which can be used to transmit control signals for the purpose of activating or deactivating a write protection device of the electronic memory. The data bus is preferably an I 2 C bus, and the write protection device is controlled by an I/O module which is likewise controlled by the I 2 C bus.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/DE03/01258 which has an Internationalfiling date of Apr. 10, 2003, which designated the United States ofAmerica and which claims priority on German Patent Application number DE102 21 572.3 filed May 8, 2002, the entire contents of which are herebyincorporated herein by reference.

FIELD OF THE INVENTION

The invention generally relates to an electrical power breaker.Preferably, it relates to one having an electronic protective device andhaving an electronic memory, which is accommodated in the power breakersuch that it is physically separated from the protective device andwhich can be read and written to by the protective device, foroperational data for the power breaker.

BACKGROUND OF THE INVENTION

A power breaker of this type has been disclosed in, for example, DE 10019 092 A1. The protective device, which, in a known manner, is in theform of an electronic overcurrent release, is in this case located in afront region of the power breaker behind a control panel. On the otherhand, current transformers or current sensors, which detect measuredvalues for the current in each of the poles of the power breaker andsupply auxiliary power required for operating the protective device, arearranged on the rear side of the power breaker which is opposite thecontrol panel. A cable harness connects these two regions of the powerbreaker. The electronic memory, which serves the purpose of storingcharacteristics and conversion factors which are dependent on thephysical size and design of the power breaker, is arranged in the pathof the cable harness.

A further known application of an electronic memory which is physicallyseparated from the protective device is a rated current plug accordingto U.S. Pat. No. 4,958,252. In this case, the memory serves the purposeof recording operational events. In particular, the events include thenumber of switching operations and the level of the respectivelyinterrupted current in order to determine from this the time forrequired maintenance work to be carried out on the power breaker.

Also known is an electrical switch having an electronic protectivedevice and a memory which are connected via a parallel data bus (U.S.Ser. No. 4,996,646 A).

If an electronic memory of the abovementioned type is arranged in thepower breaker such that it is physically separated from the protectivedevice, a connection line or cable harness is required for there to becommunication between these units. In this case, the electronic memorycan be arranged in the path of the cable harness, as is described in thementioned DE 100 19 092 A1. All of the interacting components and unitsare thus subjected to the disruptive influence of the magnetic,electrical and electromagnetic fields occurring in a power breaker.Since the sensitivity of electronic components and circuits toinfluences of this type is known, shields have been fitted in order toprevent disturbances to the operation of the protective devices (U.S.Ser. No. 5,303,113).

However, the increasing requirements placed on the switching capacity ofpower breakers lead to the electromagnetic influences on all of theelectronic components of a power breaker also being increasedcorrespondingly. Although there is extensive experience in controllingthese influences, it appears to be desirable in the interest of safetyto increase the electromagnetic compatibility (EMC) in particular of theelectronic memory which is arranged separately.

In this case, at the forefront is the consideration that, in the case ofcommunication between the protective device and the memory, addressinformation as well as write and read information can be altered by aninterference field which has accidentally been greatly increased. Forexample, it may be possible for a write operation to take place insteadof a read operation without a user being capable of recognizing this. Incertain circumstances, it is possible in this way to influence thebehavior of the protective device, which can lead to undesired trippingof the power breaker or to this tripping being suppressed even though itis required.

It is obvious per se to eliminate these undesirable influences by usingthe internal write protection of the electronic memory. The memorymodules (EEPROM) have for this purpose a separate input (WC=WRITECONTROL) which cancels or establishes the write protection depending onthe potential applied, as is described, for example, in U.S. Ser. No.5,363,334. However, in a power breaker, the memory is not accessible,for example in the case of the arrangement in the path of a cableharness according to DE 100 19 092 A1.

It is therefore not possible to use a jumper which is conventionallyprovided. Even an electrical connection of the write protection input ofa memory (EEPROM) is subject to difficulties, since an additional linerequired for this purpose is not available and undesirable additionalcomplexity is required to install it retrospectively.

SUMMARY OF THE INVENTION

Against this background, an embodiment of the invention is based on theobject of using methods/devices which are as simple but as effective aspossible to significantly improve data security when using an electronicmemory in a power breaker.

According to an embodiment of the invention, an object may be achievedby the electronic memory having a write protection device which can beactivated or deactivated via a write protection input of the electronicmemory, by the electronic memory being connected to the protectivedevice via a serial data bus, and by the electronic memory having anassociated digital I/O module which can likewise be controlled by theprotective device via the serial data bus, the output of the I/O modulebeing connected to the write protection input of the electronic memoryfor the purpose of activating or deactivating the write protectiondevice.

With such a design for the electrical power breaker, there is noadditional complexity as regards the connection between the protectivedevice and the memory, since only two conductors are required for datatransmission (serial bus). In addition there are two conductors for thepower supply, meaning that in total four conductors are required. Thisnumber of conductors has also been used to date, but did not allow thewrite protection of the electronic memory to be used.

In the context of an embodiment of the invention, the data bus may be inthe form of an I²C bus.

The arrangement described in DE 100 19 092 A1, the entire contents ofwhich are hereby incorporated herein by reference, may also be used inthe context of an embodiment of the invention, specifically such thatthe electronic memory in the form of an EEPROM and the digital I/Omodule are accommodated in a common housing arranged in the path of afour-core cable harness.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail below with reference tothe exemplary embodiments described below and shown in the figures.

The low-voltage power breaker 1 shown in FIG. 1 has, in a known manner,a housing 2, in which for each pole one switching contact arrangement 3having an associated arcing chamber 4 and one drive apparatus 5 areaccommodated for the purpose of simultaneously actuating all of theswitching contact arrangements provided. Each of the switching contactarrangements 3 has an upper connection rail 6 and a lower connectionrail 7 in order to connect the power breaker 1 to a circuit. Each of thelower connection rails 7 is provided with a set of transformers 8 whichdetects the current flowing through the associated switching contactarrangement 3 and in addition supplies auxiliary power for the purposeof operating an electronic overcurrent release 10. For this purpose,each set of transformers 8 comprises a current transformer 11 and apower transformer 12.

The connection rails 6 and 7 as well as the sets of transformers 8 arelocated on the rear side of the housing 2, whereas the electronicovercurrent release provided as the protective device 10 is accessiblefrom the opposite front side of the housing 2. For the purpose ofconnecting the sets of transformers 8 to the protective device 10, acable harness 13 is provided which is laid in channels which areprovided for this purpose in the housing 2 and which bypass the driveapparatus 5 and the switching contact arrangements 3.

Proper interaction between the protective device 10 and the currenttransformers 11 requires the protective device 10 to process the currentsignals fed to it using a conversion factor which depends on the ratedcurrent for the current transformers, the physical size of the powerbreaker and, if necessary, further parameters. For this purpose it isknown to provide electrical and/or electronic modules which are referredto as the rated current plug (rating plug), the interface module or theswitch identification module and which are not arranged in theprotective device 10 itself but are connected to it as a peripheralmodule.

Some of the conventional arrangements are illustrated in FIG. 1. 14denotes here a rated current plug, for example according to DE 100 27934 A1 or U.S. Ser. No. 4,958,252. In addition, an information memory ofthe mentioned type according to EP 0 847 587 B1 (corresponds to U.S.Ser. No. 6,034,859) can be arranged on the rear side of the protectivedevice 10, as is indicated by 15. A further possibility for thearrangement of an information memory is described in DE 100 19 092 A1,according to which the information memory is arranged at 16 in the pathof a cable harness connecting the protective device 10 and the set oftransformers.

In the embodiment of the mentioned information memory as an electricallyerasable programmable read-only memory (EEPROM), according to anembodiment of the present invention significantly improved data securityis achieved using the write protection system provided in the electronicmemories. Details on this write protection system will be explained inmore detail below with reference to FIG. 2.

FIG. 2 illustrates the circuit for the electronic memory 16 arranged inthe cable harness 13. The memory is accommodated together with an I/Omodule 17 in a housing 18. Only that part of the cable harness 13 isshown which extends between the housing 18 and the protective device 10,since the part passed on to the current transformers 11 and 12 is notessential to the understanding of an embodiment of the invention. Theelectronic memory 16 is a memory of the EEPROM (electrically erasableprogrammable read-only memory) type, specifically with a designenvisaged for use with the 1 ²C bus. The I²C bus acts as a seriescontrol device for connecting integrated circuits.

Accordingly, the memory 16 has only four connections required foroperation, namely two for the power supply and two further connectionsfor data transmission. In FIG. 2, the connections envisaged for thepower supply are denoted +5V and GND, whereas the connections envisagedfor data transmission are denoted SDA (data) and SCL (clock).

As a further connection, the memory 16 has a connection /WC (writecontrol) which activates the write protection when it is subjected to ahigh level and deactivates the write protection when it is subjected toa low level, i.e. allows the memory to be written to. The fourconnections of the memory 16 are connected with corresponding conductingcores of the cable harness 13 to the protective device 10. Controlled bythe protective device 10 or using an external operating panel, or oneconnected to the protective device 10, data can thus be read to and fromthe memory 16. In particular, this may be data which contains theconversion factor of measured values for the current transformers 11 andfurther parameters relating to the design of the power breaker 1.

The memory 16 is normally provided with its basic data when the powerbreaker 1 is produced and equipped at the manufacturer's. Duringoperation, the protective device 10 refers to the stored data, i.e.reads the stored data and processes it together with the measuredvalues, supplied by the set of transformers 8, for the current fortripping purposes in the event of an overcurrent, a ground fault and ashort circuit. Changes to the power breaker 1 as regards the currenttransformers fitted to it or an altered mode of operation may be causefor the stored data in the memory 16 to be altered.

During operation of the power breaker 1 (FIG. 1), the memory content ofthe memory 16 is thus read regularly. However, this data traffic handledvia the cable harness 13, like other electronic modules accommodated inthe power breaker 1, is subject to the influence of disruptive magnetic,electrical and electromagnetic fields which emanate from thecurrent-carrying switching contact arrangements and switching arcs inthe arcing chambers 4. Similar, although weaker, disruptive influencescan emanate from adjacent power breakers considering that power breakersare often incorporated close to one another in switchgear assemblies.

Although during operation over relatively long periods of time it hasbeen established that said interference fields do not impair datatraffic between the protective device 10 and the memory 16, it cannot beruled out that, depending on the level of the interference fields and astatistical coincidence of unfavorable conditions, faults maynevertheless occur. Such a fault may be, for example, a write operationtaking place instead of a read operation. If by this means, for example,a stored value representing the conversion factor is altered, this maybe cause for tripping in the event of a current which is too low, whichcan lead to operational faults. If, on the other hand, tripping isshifted to higher current values, this may mean that safety is seriouslyimpaired.

Operations of the described type are largely eliminated according to theinvention by a write protection device being used which is provided asstandard on the memory 16. This takes place without the number ofconductors provided in the cable harness 13 needing to be increased forthis purpose. The cable harness provided having four conductors can thusbe used without any alterations. The write protection input /WC of thememory 16 is controlled by an additional I/O module 17 which has thesame design as the memory 16 for operation using the I²C bus system.Accordingly, the I/O module 17 has the same connections +5V, SDA, SCLand GND. In addition, outputs are provided which the user can use asrequired.

The write protection connection /WC of the memory 16 is connecteddirectly to one of these outputs. Owing to a connection of the writeprotection connection /WC of the memory 16 to the connection +5V via aresistor R1, the write protection is normally activated, i.e. it is notpossible for data to be read to the memory 16, if such an instructionwere to be issued erroneously owing to interference. Only when, via theI²C bus, by means of the cable harness 13 or by way of a plug apparatusfitted to the connection of the cable harness on the housing 18, acontrol command is transmitted to the I/O module 17 which deactivatesthe write protection at the input /WC of the memory 16 can the storeddata be altered or overwritten in the memory 16 or can additional databe written to said memory 16. As a result of the fact that the memory 16and the I/O module 17 are accommodated in the immediate vicinity of oneanother within the housing 18, it can be assumed from this that faultsowing to this circuit module being directly subjected to interferencefields are improbable.

Where the memory 16 arranged in the path of the cable harness 13 isdescribed above, this is merely to be understood as an example forconnection of memories arranged at another point in the power breaker 1.The memories 14 or 15, which are likewise arranged such that they arephysically separated from the protective device 10, can thus be combinedin the same manner with an I/O module 17 and as a result protectedagainst faulty writing by way of the control via the I²C bus.

LIST OF REFERENCE NUMERALS

-   1 Power breaker-   2 Housing of the power breaker-   3 Switching contact arrangement-   4 Arcing chamber-   5 Drive apparatus-   6 Upper connection rail-   7 Lower connection rail-   8 Set of transformers-   10 Protective device-   11 Current transformer-   12 Power transformer-   13 Cable harness-   14 Electronic memory (rating plug)-   15 Electronic memory (information memory)-   16 Electronic memory (switch identification module)-   17 I/O module

Exemplary embodiments being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the present invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

1. An electrical power breaker comprising: an electronic protectivedevice; an electronic memory, accommodated in the power breaker suchthat it is physically separated from the protective device, and which isconnected to the protective device via a serial data bus and can be reador written to by the protective device, for operational data for thepower breaker, wherein the electronic memory includes, a writeprotection device which can be at least activated and deactivated via awrite protection input of the electronic memory, and an associateddigital I/O module controllable by the protective device via the serialdata bus, one output of the I/O module being connected to the writeprotection input of the electronic memory for the purpose of at leastactivating or deactivating the write protection device as a whole by theprotective device.
 2. The electrical power breaker as claimed in claim1, wherein the serial data bus is in the form of an I²C bus.
 3. Thepower breaker as claimed in claim 1, wherein the electronic memory inthe form of an EEPROM and the digital I/O module are accommodated in acommon housing arranged in the path of a four-core cable harness.
 4. Thepower breaker as claimed in claim 2, wherein the electronic memory inthe form of an EEPROM and the digital I/O module are accommodated in acommon housing arranged in the path of a four-core cable harness.